N-alkyl-4-piperidinyl-2,3-diarylpyrrole derivatives with heterocyclic substitutions as potent and broad spectrum anticoccidial agents.

Diaryl-(4-piperidinyl)-pyrrole derivatives bearing cyclic amine substituents have been synthesized and evaluated as anticoccidial agents. Improvements in potency of Et-PKG inhibition, such as azetidine derivative 3a, and broad spectrum anticoccidial activities in feed, such as morpholine derivative 8c, have been achieved.

Isolation, structure, and coccidiostat activity of coccidiostatin A.

Coccidiosis is one of the more common and costly diseases in poultry that is caused by various Eimeria species. In our quest to discover coccidiostats from natural products, we discovered a microbial fermentation extract that exhibited in vivo anticoccidial activity. Fractionation of this extract led to the discovery of two potent antiprotozoals, emecorrugatin A (1) and coccidiostatin A (2). The former compound exhibited only in vitro activity, whereas the latter new compound exhibited in vivo activity against Eimeria species in chickens at 150 ppm dosed in chicken feed. The isolation, structure elucidation, relative configuration, and activity of coccidiostatin A (2) are described.

Synthesis and SAR studies of potent imidazopyridine anticoccidial agents.

Diaryl imidazo[1,2-a]pyridine derivatives, such as 6a and 7i, have been synthesized and found to be potent inhibitors of parasite PKG activity. The most potent compounds are the 7-isopropylaminomethyl analog 6a and 2-isopropylamino analog 7i. These compounds are also fully active in in vivo assay as anticoccidial agents at 25 ppm in feed.

Synthesis and SAR of 2-(4-fluorophenyl)-3-pyrimidin-4-ylimidazo[1,2-a]pyridine derivatives as anticoccidial agents.

Compounds 10a-10d and 10i are very potent inhibitors of Eimeria tenella cGMP-dependent protein kinase (0.081-0.32 nM) and are very efficacious antiparasitic agents in vivo when administered to chickens at 12.5-25 ppm levels in the feed.

Synthesis and SAR studies of diarylpyrrole anticoccidial agents.

2-(4-Fluorophenyl)-3-(4-pyridinyl)-5-substituted pyrroles were prepared and evaluated as anticoccidial agents in both in vitro and in vivo assays. Among the compounds evaluated, the dimethylamine-substituted pyrrole 19a is the most potent inhibitor of Eimeria tenella PKG (cGMP-dependent protein kinase). Further SAR studies on the side chain of the 2-pyrrolidine nitrogen did not enhance in vivo anticoccidial activity.

Synthesis and SAR studies of very potent imidazopyridine antiprotozoal agents.

Compounds 10a (IC50 110 pM) and 21 (IC50 40 pM) are the most potent inhibitors of Eimeria tenella cGMP-dependent protein kinase activity reported to date and are efficacious in the in vivo antiparasitic assay when administered to chickens at 12.5 and 6.25 ppm levels in the feed. However, both compounds are positive in the Ames microbial mutagenesis assay which precludes them from further development as antiprotozoal agents in the absence of negative lifetime rodent carcinogenicity studies.

Hydroxylated N-alkyl-4-piperidinyl-2,3-diarylpyrrole derivatives as potent broad-spectrum anticoccidial agents.

Diaryl-(4-piperidinyl)-pyrrole derivatives bearing hydroxylated N-alkyl substituents have been synthesized and evaluated as anticoccidial agents. High potency in Et-PKG inhibition and broad-spectrum anticoccidial activities have been observed on compounds, such as 4b and 5h, which are fully efficacious in vivo at 50 ppm in feed.

Synthesis and SAR of 2,3-diarylpyrrole inhibitors of parasite cGMP-dependent protein kinase as novel anticoccidial agents.

Several analogs of 2,3-diaryl pyrroles were synthesized and evaluated as inhibitors of Eimeria tenella cGMP-dependent protein kinase and in in vivo anticoccidial assays. A 4-fluorophenyl group enhances both in vitro and in vivo activities. The most potent analogs are the 5-(N-methyl, N-ethyl, and N-methylazetidine methyl) piperidyl derivatives 12, 23, and 34. These compounds have a broad spectrum of activity. Based on the in vivo efficacy and cost of synthesis, the N-ethyl analog 23 was chosen as a novel anticoccidial agent for a field trial.

Purification and molecular characterization of cGMP-dependent protein kinase from Apicomplexan parasites. A novel chemotherapeutic target.

The trisubstituted pyrrole 4-[2-(4-fluorophenyl)-5-(1-methylpiperidine-4-yl)-1H-pyrrol-3-yl]pyridine (Compound 1) inhibits the growth of Eimeria spp. both in vitro and in vivo. The molecular target of Compound 1 was identified as cGMP-dependent protein kinase (PKG) using a tritiated analogue to purify a approximately 120-kDa protein from lysates of Eimeria tenella. This represents the first example of a protozoal PKG. Cloning of PKG from several Apicomplexan parasites has identified a parasite signature sequence of nearly 300 amino acids that is not found in mammalian or Drosophila PKG and which contains an additional, third cGMP-binding site. Nucleotide cofactor regulation of parasite PKG is remarkably different from mammalian enzymes. The activity of both native and recombinant E. tenella PKG is stimulated 1000-fold by cGMP, with significant cooperativity. Two isoforms of the parasite enzyme are expressed from a single copy gene. NH(2)-terminal sequence of the soluble isoform of PKG is consistent with alternative translation initiation within the open reading frame of the enzyme. A larger, membrane-associated isoform corresponds to the deduced full-length protein sequence. Compound 1 is a potent inhibitor of both soluble and membrane-associated isoforms of native PKG, as well as recombinant enzyme, with an IC(50) of <1 nm.